The present invention relates to an electrostatic lens used for a charged beam such as an electron beam, ion beam, and the like, an electron beam lithography apparatus and charged beam applied apparatus using the lens, and a device manufacturing method using these apparatuses.
In recent years, LSI patterns have been increasingly miniaturized, and in the DRAM field, device integration has progressed like 256M, 1G, and 4G DRAMs after development of 64M DRAMs. An exposure technique is a very important one of micropatterning techniques, and especially, an electron beam lithography technique can achieve micropatterning of 0.1 xcexcm or less, and is expected as one of future exposure means.
A conventional electron beam lithography apparatus used adopts a single-beam lithography scheme such as a Gaussian beam scheme, variable shaped beam scheme, and the like. These lithography schemes are used in application fields of mask write, research and developments of ultra LSIs, and ASIC devices which are produced in small quantity.
Recently, the electron beam technique has been studied and developed, and a new multi-beam lithography method which can improve the write speed using a plurality of electron beams has been proposed and studied as a scheme for an electron beam lithography apparatus which can improve productivity and can be used in the manufacture of memory devices such as DRAMs and the like. In order to obtain a throughput of 30 to 40 wafers/hour required in the manufacture of semiconductor devices in this multi-beam rendering scheme, several hundred or more beams are required as multi-beams. Therefore, a technique for forming a multi-lens with high layout density by reducing the size of electron lenses is important.
FIG. 6A shows an example of a typical microlens (K. Y. Lee, S. A. Rishton, and T. H. P. Chang, xe2x80x9cHigh aspect ratio aligned multi-layer microstructure fabrication, J. Vac. Sci. Technology B12(6), 1994, 3425) manufactured using a silicon semiconductor process. In this example, an electrostatic lens is formed by bonding electrode substrates 51 to 53 each having a lens aperture 9 and Pyrex glass plates 54 and 55 to an Si substrate by anodic oxidation bonding.
FIG. 6B shows an example of a multi-lens comprised of a plurality of electrostatic lenses fabricated using Si substrates 61 to 63 and Pyrex glass plates 64 and 65 prepared by the aforementioned method. Fabrication of these electrostatic lenses using a semiconductor process is considered as an effective method in terms of miniaturization, shape precision, and layout precision.
However, an electrostatic lens of this type suffers the following problem. That is, the conventional electrostatic lens shown in FIG. 6A uses insulators as spacers between electrodes, and has a shape with which the insulators around the lens are directly observed from a beam axis 11 where an electron beam passes. Therefore, since an electron beam is readily influenced by charge-up of the insulator side walls due to electrons and ions scattered into the lens aperture, the on-axis potential in the electrostatic lens becomes unstable, and results in beam position drift and deteriorated lens focusing characteristics. Furthermore, when a multi-lens is formed by decreasing the layout spacings of a plurality of electrostatic lenses, crosstalk of electric fields due to electrodes and wiring is produced.
As a conventional method of preventing charge-up of an electrostatic lens, a structure in which insulators 74 and 75 are not directly observed by bending electrodes 71 to 73, as shown in FIG. 7, is used. This method is effective for preventing not only charge-up of an electrostatic lens but also crosstalk, but it is difficult for that method to improve the degree of integration by miniaturizing a multi-lens due to the complicated electrode shape.
The present invention has been made in consideration of the conventional problems, and has as its object to provide a compact multi-lens type electrostatic lens which has high beam position stability and lens focusing characteristics, is free from any influence of crosstalk between lenses, and has a high degree of integration, an electron beam lithography apparatus and charged beam applied apparatus with high productivity using the lens, and a device manufacturing method using these apparatuses.
In order to achieve the above object, a first multi-lens type electrostatic lens of the present invention is characterized by comprising a lens electrode substrate which is formed by stacking at least two substrates each having a plurality of lens apertures, an inner wall of each of which is formed by a high-resistance portion along a beam axis of a beam emitted by a beam source, and which has an electrode bonded around the plurality of lens apertures between the substrates, and low-resistance portions which have apertures corresponding to the plurality of lens apertures and are bonded to two surfaces of the lens electrode substrate.
A second multi-lens type electrostatic lens is characterized in that, in the first multi-lens type electrostatic lens, the high-resistance portion is made up of high-resistance layers formed on inner walls of apertures formed in an insulating substrate, each of the low-resistance portions is formed by forming apertures corresponding to the lens apertures in a low-resistance substrate, and stacking the low-resistance substrate on the insulating substrate, and wiring for the electrode is formed via the insulating substrates stacked on the two sides of the electrode.
A third multi-lens type electrostatic lens is characterized in that, in the first or second multi-lens type electrostatic lens, a plurality of electrostatic lenses equivalent to the electrostatic lens are independently controlled.
A fourth multi-lens type electrostatic lens is characterized in that, in any one of the first to third multi-lens type electrostatic lenses, a plurality of electrostatic lenses equivalent to the electrostatic lens are laid out to form a face-centered structure.
A fifth multi-lens type electrostatic lens is characterized in that, in the second multi-lens type electrostatic lens, the low-resistance substrate is located on an outermost side to sandwich the insulating substrate, and a thickness T thereof and a diameter D of the aperture satisfy T greater than 0.3D.
A sixth multi-lens type electrostatic lens is characterized in that, in any one of the first to fifth multi-lens type electrostatic lenses, a resistance of the high-resistance portion is not constant along a beam axis direction.
A seventh multi-lens type electrostatic lens is characterized in that, in any one of the first to sixth multi-lens type electrostatic lenses, a resistance of the high-resistance portion has a positive differential coefficient along the beam axis.
An eighth multi-lens type electrostatic lens is characterized in that, in any one of the first to seventh multi-lens type electrostatic lenses, a plurality of electrodes equivalent to the electrodes are present in a beam axis direction, and arbitrary potentials can be respectively applied to the plurality of electrodes.
A ninth multi-lens type electrostatic lens is characterized in that, in the eighth multi-lens type electrostatic lens, a differential coefficient of a gradient of a voltage applied to the plurality of electrodes present in the beam axis direction is positive in an acceleration lens system and is negative in a deceleration lens system along the beam axis.
A 10th multi-lens type electrostatic lens is characterized by further comprising temperature-controllable cooling means in any one of the first to ninth multi-lens type electrostatic lenses.
A 11th multi-lens type electrostatic lens is characterized in that, in any one of the first to 10th multi-lens type electrostatic lenses, a resistivity of the high-resistance portion falls within a range from 106 xcexa9cm to 109 xcexa9cm.
A 12th multi-lens type electrostatic lens is characterized in that, in any one of the first to 11th multi-lens type electrostatic lenses, the high-resistance portion consists of any one of silicon carbide, a nitrogen compound, and cladglass.
An electron beam lithography apparatus of the present invention is characterized by using any one of the first to 12th multi-lens type electrostatic lenses.
A charged beam applied apparatus of the present invention is characterized by using any one of the first to 12th multi-lens type electrostatic lenses.
A device manufacturing method of the present invention is characterized by comprising the step of applying a resist on a substrate, the step of directly writing a pattern on the substrate using an electron beam lithography apparatus or charged beam applied apparatus of the present invention, and the development step of developing the substrate, the electron beam lithography apparatus or charged beam applied apparatus comprising a lens electrode substrate which is formed by stacking at least two substrates each having a plurality of lens apertures, an inner wall of each of which is formed by a high-resistance portion along a beam axis of a beam emitted by an electron beam source, and which has an electrode bonded around the plurality of lens apertures between the substrates, and low-resistance portions which have apertures corresponding to the plurality of lens apertures and are bonded to two surfaces of the lens electrode substrate.
In these arrangements of the present invention, since the inner wall of the lens aperture is formed by an electrode and a high-resistance portion joined to the electrode, and a low-resistance portion joined to the high-resistance portion is provided on the side opposite to the electrode, even when a scattered beam strikes the inner wall, the charge is relieved via the high-resistance portion, thus preventing charge-up in the lens aperture by a simple arrangement. Also, crosstalk between electric fields of neighboring electrostatic lenses can be prevented by the shield effect of the high-resistance portion. Hence, the degree of integration of electrostatic lenses can be improved, and the productivity in the manufacture of devices can also be improved.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.